More Commands

system info

hostname # shows hostname uname # shows UNIX name uname -a # (all) shows more information uptime # shows how long system has been running and CPU load averages quota # shows disk quota (if any) on your account df -h # shows disk space free in each mounted filesystem, human readable du -hs /etc # shows disk space used in specified directory # error messages from insufficient permissions du -ks /etc 2> /dev/null # kilobytes, discards error messages free # shows memory use (Linux only) sensors # shows temps, fan speeds, etc. (Linux only) vmstat # shows virtual memory use less /proc/meminfo # detailed memory info q # quit less less /proc/cpuinfo # detailed CPU info q # quit less ls -d /proc/[a-z]* # more info

dates

date # shows time and date date +%s # seconds since epoch (Jan 1 1970), many other format options cal # shows calendar for current month cal 4 2025 # shows calendar for Apr 2025 cal 2025 | less # shows calendar for all of 2025 CE q # quit less cal 3 | less # shows calendar for all of 3 CE q # quit less

user info

whoami # shows your login name id # shows UserID, GroupID, and groups users # (similar to who, finger) shows users logged in w # shows uptime, users logged in, and what they're doing finger $USER # this shows information about you chfn # (change full name) enter your password and full name when prompted # just press the Enter key after the other prompts cat > .plan # write a .plan file # type a few lines of information about yourself ^D # terminate cat command finger $USER # now shows the full name and .plan finger stuart # this shows another user last | less # shows recent logins q # quit less

file utilities

tree /usr | less # list in tree format q # quit less when done tree -d /usr | less # show directories only q # quit less when done tree -L 1 /usr | less # (numeral 1) show 1 level only q # quit less when done wc /etc/passwd # count lines, words, characters wc -l /etc/passwd # lines only wc -w /etc/passwd # words only wc -c /etc/passwd # chars only wc -L /etc/passwd # length of longest line file /etc/fstab # ASCII text file /bin/gunzip # shell script file /bin/ls # ELF 32-bit LSB executable (binary) file /usr/man/man1/less.1.gz # gzip compressed data (man page for less) od -ta /etc/fstab # shows non-printing chars as char names od -tc /etc/fstab # shows non-printing chars as C escapes strings -n16 /bin/dash | less # 16+ consecutive printing chars (in binary file) q # quit less cat > foo-0 # create a file (original) line 1 lime 2 # misspelled Ctrl+d cat > foo-1 # create another file (new and improved) line 1 line 2 # corrected Ctrl+d diff foo-0 foo-1 # show differences between two files (line editor format) diff foo-0 foo-1 | tee foo-bar.diff # create and display update file cmp -l foo-0 foo-1 # binary compare, -l shows which bytes differ shred -n1 foo-0 # one pass, overwrite with random bytes, -z overwrites with zero bytes od -tc foo-0 # garbage rename foo- foo0- foo-* # pattern, replacement, file(s) ls foo-*

rm foo* test.bin # clean up